The present invention concerns the performance management and traffic control of what are known as asynchronous transfer mode (ATM) networks.
The arrival of broadband networks heralded by the introduction of optical fibres has substantially increased the range and nature of data which can be transmitted over telephone lines. Thus while some users may be content with merely maintaining voice connections at constant bit rates, other users might wish to have access to other connection types such as video and data at variable bit rates. Thus users now require the ability to select from a number of connection types in accordance with their needs. ATM networks have been developed to meet this demand. In a typical case a user can choose between three potential connection types, namely the already mentioned two megabit voice links, a variable bandwidth link peaking at 10 megabits and with a mean of 5 megabits, and a third variable bandwidth link peaking at 20 megabits and having a mean of 8 megabits. The second of these connection types can be used for high speed data transfer and the third for the transmission of video images. It will however be appreciated that the present invention is not limited to any particular set of connection types.
FIG. 1 of the accompanying drawings is a functional representation of user and service interaction in a typical ATM network environment. Layer 100 represents the users and layer 101 represents suppliers who provided value added services to users. Layer 102 gives some examples of value added network services such as additional telephoning features, provision of video data, transfer of data files and the like, and layer 103 shows the various functional layers of the actual ATM network.
The basic unit of an ATM network is the ATM switch. Such a switch will be described in greater detail hereinafter but each switch supports several hundred users and provides the requisite links between the users and other ATM switches in the network. In order to maximise the potential bandwidth available to users the telecommunications industry has developed what are known as virtual path (VP) networks. VP networks differ in two ways from the traditional telephone network. In a traditional telephone network when a user wishes to access another user a fixed channel is established via the various nodes and switches and this channel either has the ability to carry the data or not. In a VP network each user is allocated a bandwidth appropriate to his assumed needs in the various connection types and the ATM network management provides bandwidth by selecting a route from all of the available paths in the network. Of course each user will have a usage pattern which will be only partly predictable. It will be appreciated that it would be uneconomic to provide each user all the time with all of the maximum bandwidth that that user might require. Accordingly, in a VP network the sum of the nominal bandwidths allocated to the users connected in the network is substantially greater than the total bandwidth of the network. Thus if every user utilised its bandwidth to the maximum at the same time the network would be unable to cope. Accordingly, a major problem with the management of ATM networks involving virtual paths is to balance the requirement to utilise the capacity of the network to its maximum whilst at the same time maintaining the quality of service (QoS) offered to the subscribers to the network. Fundamental attributes of QoS are delay, loss and delay variation.
When discussing ATM networks certain terms have become standard. Thus a link is an ATM transmission path which provides bandwidth between transmission end points. Normally such a link will be a fibre optic one. A number of transmission paths and transmission end points form the transmission capability of the network which is provided to the virtual path (VP) level. The transmission end points are ATM switches which route traffic over VP links.
A concatenation of VP links is terminated by VP connection end points to form VP connections which are simply called VPs in the remainder of this specification. VPs enable the ATM transport network to provide either teleservices to end users via the network service service suppliers at layer 102. In each of these cases, a set of VPs are provided to the VC level such that at this level, VPs are interconnected by VC links. The resulting concatenation of VC links form a VC connection which are used to transport these teleservices. Nodes, links and VP""s can all be considered as network resources and in a typical network each is represented by a distributed object. Thus information concerning the network can be obtained by calling function acting on these distributed objects. The importance of this arrangement to the present invention will become apparent hereinafter.
More than one connection is usually used to provide an end-to-end service association or call to a user/customer of the network. Each of the connections in a call have certain characteristics such as bandwidth utilisation profile and performance targets that it shares with other connections of the same type.
The performance management of a network layer can be broadly classified into two groupsxe2x80x94Network Resource Management (NRM) and Traffic Control Management (TCM). NRM deals with VP bandwidth management, VP routing, virtual channel (VC) routing strategies, VP and link load balancing, VP Topology Management and quality of service (QoS) verification. However the performance management in ATM networks is an extremely complex problem due to many factors. Amongst these are the fact that each user has the potential of a plurality of connection types and because of the VP model of the network the combination of the number of different connection types with the number of potential virtual paths between the ATM switches in the network rapidly becomes extremely large. Adding to the problem is the variability of the traffic characteristics and controls at many levels together with the necessity to plan ahead for substantially larger networks. Thus in an ATM network Virtual Path Bandwidth Management (VPBM) is both a very important function and one which in practice is difficult to carry out.
In dealing with the above problems in VPBM, it must be borne in mind that the theory of performance management functionality as part of an integrated Telecommunications Management Network (TMN) using ATM switches and virtual paths is in general not well understood. This contrasts with the well-founded mathematical models such as queuing theory, etc., for assessing and analysing the performance of orthodox telephone networks.
To summarise, virtual path bandwidth management as applied to ATM networks is a network management function which aims to ensure that virtual paths have the right size, allocation and route. The difficulties of carrying out this function include:
the vast number of virtual paths needed for future public ATM networks leading to a need for scalable algorithms and implementations;
impossibility of accurate traffic models for future servicesxe2x80x94ATM networks allow applications to produce traffic at continuously varying rates preventing accurate models needed for optimal solutions and changing business requirements. Thus, network providers want to be able to easily modify how they control their networks. For example a provider may want to offer more reliable QoS, with corresponding lower network utilisation, at premium times than at economy times. This requires algorithms for bandwidth tuning which can be adapted to change policies. Additionally there is a lack of accurate traffic models on which such algorithms can be based.
A known approach in dealing with the problem of monitoring traffic in ATM networks and adaptively changing the bandwidths of VPs to accommodate the required load of VCs is a centralised one in which for bandwidth allocation only the VP termination points are involved. The telecommunication management network (TMN) decides the bandwidth required and downloads this information to the VP termination points. However with increasing network sizes the computing power required to carry out effective adaptation of the bandwidth allocation becomes too great and the time penalties involved become too severe to enable the network to be updated except at relatively long intervals and with great effort.
An article entitled xe2x80x9cFast VP-Bandwidth Measurement ith Distributed Control in ATM Networksxe2x80x9d in IEICE Transactions on Communications, vol E77-B, No 1, Jan. 1, 1994 pages 5-14 discloses a management system where the control is carried out within the switches. A similar switch based system is disclosed in an article entitled xe2x80x9cServing Humanity Through Communicationsxe2x80x9d, Supercomm/ICC New Orleans, May 1-5, 1994, Institute of Electrical and Electronics Engineers, pages 44-50.
Neither of these documents provides a solution to the problems set out hereinbefore.
The present invention is concerned with providing a solution to the above problems. Thus one concern of the present invention is to provide a system for managing bandwidth in an ATM network.
However a solution concerning bandwidth cannot by itself deal with all potential problems of ATM management. A major problem can arrive when the distributed agents have to deal with the following situation. This is when for a particular link:
a) The link capacity has all been reserved by the VP""s it carries.
b) All the VPs it carries are using all their reserved bandwidth.
c) One or more of those VPs require more bandwidth than their currently reserved bandwidth.
Thus the present invention is concerned with providing a generic approach to a range of problems in ATM management.
In accordance with one aspect of the present invention there is provided a management system for an ATM virtual path network in which the physical connections are provided by broadband links between ATM switches, and comprising means for measuring current network load in individual links and virtual paths, and sets of inter-communicating distributed agents for carrying out management in response to measured load and management requirements.
In accordance with a second aspect of the present invention there is provided a method of managing an ATM virtual path network in which the physical connections are provided by broadband links between ATM switches, and comprising measuring current network load in individual links and virtual paths, and utilising sets of inter-communicating distributed agents for carrying out management in response to measured load and management requirements.